Induction heat treating apparatus



April 28, 1942. H. E. soMEs 2,281,293

INDUCTION HEAT TREATING APPARATUS original Filed Aug. 17, 1936 5 sheets-sheet 1 April 28, 1942. H. E. soMEs INDUCTION HEAT TREATING APPARATUS 5 Sheets-Sheet 2 INVENTOR ATTORNEY Original Filed Aug. 1'7, 1936 II IILLI|IIHIIIIII l IIIIIII IIIIL April 28, 1942.v H, E. soMEs 2,281,298

INDUCTION HEAT TREATING APPARATUS Original Filed Aug. 17, 1936 Sheets-Sheet 3 w s. m

m m R Af V w /m m T G. M m E. i A rO 'Il Y 8 lll"" w M l I El. m

April 28, 1942. H. E. sMEs INDUCTION HEAT TREATING APPARATUS 5 Sheets-Sheet 4 Original Filed A g. 17, 1956 NVENTOR Howard E Somes BY Www ATTORNEY April 28, 1942. H. E. soMEs INDUCTION HEAT TRETING APPARATUS Original Filed Aug. 17, 1936 5 Sheets-Sheet 5 INVENTOR Hasard E. Somes M AL fri/M ATTORNEY Patented Apr. 28, 1942 INDUCTION HEAT TREATING APPARATUS Howard E. Somes, Detroit, Mich., assignor to Budd Induction Heating, Inc., Philadelphia, Pa., a corporation of Michigan Original application August 17, 1936, Serial No.

1941, serial No. 400,623

' (ci. 21e- 13) 18 Claims.

This application is a division of my copending application Serial No. 96,346, tiled August 17, 1936, for Induction heat-treating apparatus.

The subject matter ol' the present invention divided irom my copending application Serial No. 96,346 relates to a machine for automatically carrying out heat treatment oi metallic products, and in particular to the induction heating head or tool and manner of operating the same with respect to the workpiece, the object being to provide an induction heating tool and associated Darts so arranged as to improve the emciency of its electric and magnetic circuits and the cooling of these elements, the ultimate aim being that of improving the eillciency o! heat; treating through the medium of electro-magnetically in-.

duced heating currents.

With the above and other objects in view, the present invention consists in certain features of construction and combinations of parts to be hereinafter described with reference to the accompanying drawings and then claimed.

In the drawings which illustrate suitable embodiments of the invention:

Figures 1 and 2 are side elevation and iront elevation views, respectivelyl of the machine;

Figures 3 and 4 are, respectively, vertical crosssections of the heating, quenching and switching units, Figure 3 showing the quenching unit in engagement with the workpiece while the heating unit is out of association therewith, and Figure 4 showing the heating unit in association with the workpiece, the switching unit having appropriately coordinated relation in each case;

Figure 5 is an enlarged section taken substantially on the line 5 5 ot Figure 4;

Figure 6 is an enlarged vertical cross-section of the workpiece and the quenching and heating units, showing certain details of lnterrelation, particularly the relative axial mountings, the section being taken substantially on the line 6-6 of Figure 5;

Figure 7 is a view similar to Figure 6, showing the quenching head alone associated with the workpiece and its operative relation with respect thereto;

Figure 8 is a section taken substantially on the line 8--8 of Figure 7;

Figure 9 is a longitudinal section of a modified form of heating coil and quenching head; and

Figure 10 is a section taken substantially on the line lil-l0 of Figure 9.

Referring to the accompanying drawings in which like numerals refer to like parts throughout the several views, the several Component Divided and this application July 1,

mechanisms of the machine are all mounted upon a machine frame 20 in the form of a tall column oi rectangular form (see Figures 1 and 2) rhaving an extended base 2|. This base and column are preferably constructed of steel fusion welded: together to form a generally hollow rectangular column open at the back as shown in dotted lines in Figure 1. The workpiece mounting mechanism, generally designated M, the heating unit mechanism generally designated H, the transformer power switching mechanism generally designated T and the quenching unit generally designated Q. together with their immediate appurtenances and motor operating mechanisms, are mounted upon the front tace of column 20, being supported therefrom by suitable removable and adjustable brackets as clearly appears, the brackets being connected to the i'ace o'f the column by appropriate bolt and nut connections and in the instance of the mounting mechanism provided with a vertical sliding and screw adjustment 22-23. The servo-motor for raising and lowering the heating unit is designated H1 and is mounted vertically next above the transformer switching unit T and connected therewith and with the heating unit H by means of a hollow piston rod 24. The motor for operating, by means of a second piston rod 25, the quenching unit Q is located vertically next above the motor H1 and is designated Q1.

Interiorly of the column 20 from bottom to top are arranged respectively an accumulative system Q2 for the supply of cooling medium tothe quenching unit Q, capacitance 'li'z which is a part of the switching unit T, and the control unit C for the machine as a whole.

The workpiece being operated upon in the illustrated form of my invention is a hub 26 of an automobile wheel. The mounting mechanism M is especially adapted to it. Mechanism M comprises a horizontal table 2l supported by an under annular bracket 28, the vertical branch 29 of which is slidably mounted 'upon the face of column 20 by means of vertical ways of the order oi those found upon the tables and heads oi machine tools. Vertical adjustment is provided as heretofore indicated, in the iorm of a screw 23 which engages the under side of the vertical branch 29 of the angle bracket 28.

The hub is received upon vertically extending centering studs 3| which engage in holt holes in the wheel or brake drum or mounting llange 33 of the hub, the holes being accurately drilled for the centering operation and the under side oi flange 33 being properly faced to atl'ord to the hub true vvertical alignment of its axis when it rests upon the skirts 34 of the studs 3l carried by table 21. f course, other means of centering may be provided, but these are among those ccmmonly used in connection with automobile hubs and wheels.

Suitable mechanism described and more clearly shown in my copending application aforesaid is mounted beneath the table 21 for securely holding the workpiece 2l in place. It is to be noted that the barrel of the workpiece or hub 2i extends into a hollow box-like member 4l, which receives and conducts from the workpiece f through a conduit Il to the tank Il of the accumulator Q the quenching iiuid which has been distributed through the quenching mechanism Q.:

'I'he heating unit H is comprised of a heating coil and appurtenant parts. The construction in general is that described and claimed ln my copending application Serial No. 50.829, med November 2l, 1935, now Patent No. 2,256,873,

dated September 23, 1941, and need not theref fore be described in greatestdetail vhere except in the matter of the improvements disclod herein. In general, the` coil Il is of a diameter and length adapting vit to be projected within the hollow of the large barrel Il of the hub and in close'. juxtaposition to the surface I4, which surface is the surface to be heat treated. The sur face I4 is machinedto serve as a bearing race forthe hub. It is to be heat treated to serve as such race as effectively as a hardened ball race. High-frequency alternating current is to be supplied the heating coil to heat treatv surface I4 to harden it to a desired depth. This depth is usually' buta small fr'action of `the total wall thickness of the' hub barrel l5.

The coil Il is carried upon a 'spool-shaped yhollow inner laminated core II of magneticlmaterial. The laminations are mounted by dovetail connection upon a `hollow arbor I1 of nonmagnetic material. This arbor is really a part of 4the hollow piston rod 24 to the heatinglmit from passage therethrough of immense quantities ofj power andthe extreme heat developed in 'the workpiece 28 while it is juxtaposed thereto.

Coacting with the core Il of the heating unit H is an axially deep ring 1l of magnetic material coaxially mounted. This ring 1l, as shown in Figures 3 and z4, is solid andi radially 'slotted partly throughv from the inner surface. Ipropose also, as in the modification shown in Figure 9, to make it of laminaticns. All-important isl the fact that its lowerend 1ifis provided with a recessedportion 12 complementa! to the recessed portion 13 of the upper or outer end of the hub barrel il whereby when the heating unit H is lowered into functional relation with the workpiece 26, the lower end 1I of the ring 1I engages the upper end of the hub. barrel Il with the recessed portions 12-13 in complemental engagement, and the lower end 1|y in close juxtaposition whereby the magnetic flux passes from the upper ends of the laminationsofcore into the lower ends 1i of the ring 10 and therethrough to the complemental portions 12-13 into the body of the hub barrel 65. Air gaps which might other- Y progressively as the work coil 63 moves upward- 1y from the workpiece 26, takes the magnetic place of the barrel B of the hub and thereby minimizes changes in power factor'relations in Y the vworir circuit, and thirdly for the purpose of hollow' piston rod 24 by means of the inwardly tion 14 between the upper end of the ring 1l and a ange ring 15 fixedly mounted on the piston rod 24a distance vertically above coll `63. The

upper end of ring 10 is slidably mounted upon the projecting flange or ring connection 18 shown in the form of a. separate ring having a pin con'- nection with the upper end of the ring 10.` An inner and supplemental sliding guide and bearing 1Q is provided'in the form of a ring clamped in iixed relation to the arbor 61 by means of a threaded clamping ring 19. Therebyas the work coil Slis moved into functional relation with the workpiece 26, the supplemental magnetic ring 1l engages the outer end of the hub and is stopped thereby, and as further movement of the coil I3 toward its ilnal position with respect to the workpiece takes place, the piston rod 24 slides through the upper bearing 18 of the ring 1l and the guidering 18 slides along its interior, the spring 14 being progressively compressed to firmly hold the supplemental ring 10 in position upon the end of the hub barrel.

The mmm-.torv sa. supplying the ycou u, is

with the upper end of the inner hollow core I6,

passed through the xed ring 15 of the piston rod 24 and slidable vertically through the relatively movable mounting Vflange 1l of the ring i 1l to reach the upper end of the coil II. Cool- 50 ing water traversing the coil 63 emerges from the lower end ofthe coil by way of an angular duct IB throughthe' lower end of the arbor t1 to find its way into anaxially upwardly extending channel BI formed by a recess in the inner surface B2 of the hollowpiston rod 24. This hollow l extends as far as the fixed mounting flange 1Swhere, as shown in detail in Figure'6, it enters a bore l2' formed in the ring 1I and from this bore finds its way to the hollow ofconductor 69 and thence back to the source of water supply. This channel 80, 8|, 82 connecting with conductor 6 9 constitutes also through its several parts and the walls thereof. the return current conductor for the coil u.

Theswitching mechanism T next above `the heating unit H in axial augment is a transformer switching device. This also is described in my copending application SerialNo. 96,929,r

filed August 17, 1936, and claimed therein, and needs but a general description here, over and above those novelties and its combinations with the heating and quenching units H andl Q. The mounting of this unit T on the face of a column `2l isby means of an outstanding bolted-on bracket 83.- This bracket is of non-magnetic material and embodies the cylindrical casing Il of the transformer switching unit T: 'Ihis cylindrical casing is provided with upper and lower clamping heads or rings Il. It which retain in place the laminated magnetic core l1 of the primary element of the transformer unit. These laminations are retained in place through annular ribs Il which enter complemental notches in the laminations of the core I1. Ihe primary winding of this element is designated Il and is comprised of a suitable number of turns o! hollow watercooled conductors as indicated, the leads of which Il and Il are brought out to connect with the primary supply circuit. These leads are brought out through spaced radial laminations and intervening sector-shaped blocks of insulated material n.

The secondary element of this transformer switching unit is comprised of a laminated magnetic core n and accompanying secondary coil Il together with an appendant core extension Sl. The core laminations in this case are retained in cylindrical radial order by means of upper. and lower clamping rings or heads It and l1 which engage the lamlnations by a system 'of annular ribs and complemental recesses designated 9| and essential!" similar totho I8 in connection with the primary element. The annular ring It is really in the form of a shoulder or i'iange upon the hollow piston rod 2l, which, at its bottom end through the arbor or shank portion supports the heating unit H. 'Ihis piston rod Il as is nowapparent is made in a number of sections screw-threaded or otherwise connected together in through axial alignment. It is upon the center ofl these sections of piston rod 24 that the secondary elements of the transformer switching device are mounted as described, and the ring Il is in the form of an integral shoulder extending from the lower endk of this center section. Ring l1 is in the form of a ring or flange centered about the upper end of the central section of piston rod 24 and clamped in position by through-running clamping bolts il which extend through the hollow of the magnetic core between that core and the piston rod 24 and have a threaded engagement with the lower clamping ring Ring s1 has a key and slotconnection Ill which preserves its angular position with respect to the lower ring whereby the bolts and the conductor connections shortly to be described are maintained in axial parallelism. `The extension Il is in the embodiment shown an integral extension from the laminations of the main body of the core iuxtaposed to the secondary coil Il, and is provided with a downwardly divergent air gap. between it and the primary coil t! when in raised position as shown in Figure 6.

'Ihe work circuit connections between the secondary or working coil oi.' the transformer switching device T and the coil I8 of the heating unit are eilected through the hollow of the core il. Insulation sheathed tubular conductors III and Il! are projected through apertures in axial alignment through the two clamping rings II and I1 and insulated therefrom. They are retained iirmly in position by threaded-on nuts III, and suitably insulated from the clamping rings. At their lower ends they are connected by union adaptors. One of these adaptors I is of a type changing from the rectangular cross-section of the conductor il constituting the upper tercates therewith through the channel Il.

minalofcoililtothecircularcross-section of the conductor III. The other is a circular adaptor, since the winding of coil Il is not integrally extended to the head Il but communi- At their upper ends thev tubular conductors Ill. Il! are connected through flexible insulating leads lli with a source of cooling water supply, which, during operation of the machine, is constantly circulated through the heating coil of unit H. Intermediate their upper and lower ends conductors III, il! are connected by manii'olds i which break info the insulated coverings of these conductors and communicate by apertures Ill with the water conveying interior thereof, in multiple with a number of turns oi' the secondary coil M, in the instance shown four coils, as indicated by the dotted line. through running connections Ill. Secondary Il is wound in four turns in multiple and therefore consists in its twenty convolutions of but live effective turns or thereabouts. Through the multiple connections lll, not only do the con` volutions oi coil Il receive water for cooling purposes, -hut also through them coil M delivers its energy to the work circuit in which it is included. the work circuit comprehending in its lower end the work coil Il.

'Ihe uppermost section of piston rod Il as clearly appears in Figure 2 connects with the piston lll (shown in dotted lines) of the reciprocating compressed air servo-motor lil constituting the elementHl of the heating unit H. I'his motor is secured to the face of column 2l through an extension ill from the face of the column since its dimensions are small. It is a double acting motor operating through compressed air received at opposite ends of the cylinder through valve conduits Il! communicating with a piston valve H3 operated electro-pneumatically through the magnet ill. This arrangement of electro-pneumatic valve control being oi' known construction and arrangement, it s umces to say here that the arrangement is such that when the valve magnet lll is deenergised the valve is held in o! position in which air is admitted beneath the piston III to raise the same, but when the magnet valve IM is energised the valve moves to on position in which air is admitted above the piston Ill. In one case the servo-motor unit Hl of the heating mechanism operates through piston rod 24 to raise the secondary element ofthe transformer switching unit T together with the appendant heating unit H including its coil Il to the position shown in Figure 3. In the other case the magnetic valve H4 being energized operates to lower the same .units to the working positions shown in Figure 4,

in which the primary and secondary coils Il and I4 of the transformer switching unit are in working juxtaposition and the coil 68 of the heating unit and the supplemental magnet ring Il are in working juxtaposition to the workpiece Il.

Next above the servo-motor H1 of the heating unit H is the servo-motor Q1 of the quenching unit Q. This servo-motor is constructed and arranged and operated in a manner essentially similar to servo-motor Hl of the heating unit H. It would sumce, therefore, to designate its piston Hs, its cylinder m, its pinoli valve mi and its operating electro-magnet HI. In an operation entirely similar to that described in connection with servo-motor H1, in the normal spring pressed oi! position oi' valve ill, piston Hi is raised in cylinder llt, and when moved downwardly in response to a movement of valve to on position, operates through piston rod 25 whichr extends axially through the hollowpiston rod 24 oi' servo-motor H1, and through those extensions thereof which traverse the transformer switching mechanism T and the heating mechanism H, to project the spray head l I3 of the quenching unit Q into Vworking juxtaposition with the barrel 55 of the workpiece 20. This spray head consists of an extension having threaded engagement with the .lower end of the piston rod and provided with a large number'of spray apertures |2| adapted to direct quenching iluid substantially radially in a number of diierent directions upon the surface 54 to be treated.. The piston rod 25 and its downward extensions are tubular and communicate at the upper end beyond the servomotor Q1 through a flexible connection |22 with the accumulator mechanism Q in the base of the column 20 as indicated by the dotted line |23.

The piston rod'25 passes through stufng boxes |24 at opposite ends of the servo-motor Ql of the quenching unit Q, through stunlng box connection |25 at the upper end of servo-motor 1Hx of the heating unit mechanism H, through stuning box |23 on the upper side of the piston |03 of servo-motor H1, through lubricated sliding connections |21 with the transformer switching unit mechanism T, and ultimately through a lubricated lining tube |23 in that lowermost section of the operating piston rod 24 of the heating mechanism H to emerge in the spray head ||3 just now described.

This piston rod 25 of the quenching unit carries vatthe lower end of its spray head |I5, a tapered centering and aligning nxture or head of a conical shape adapting it to engage and be centered by the conical inner surfaces |23 of the small barrel. 40 of the workpiece. So centered and aligned and xed on the axisr of the machine, the piston rod 25 serves as aKA central guide for the elements of the heating mechanism H and those oi the switching mechanism T which slides up and down under the action of servomotorHl. However, it is notthe only guiding and centering means for these elements inasmuch as within the transformer switching mechanism T the core extension engages through its exterior periphery, in this instance constituted by the insulating sleeve |3|, the axially hanged cylindrical bore |32 oi the clamping head 05 thereby centering and aligning the axial movement of the secondary switching element of the mechanism. Furthermore, the upper section of the piston rod 24 is in its turn passed through the aligning stumng box |33 of the servo-motor cylinder H1, holding in position in axial alignment the upper end of the secondary element.

vIndeed the secondary element of the transformer switching mechanism T and the coil V elements of the heating unit H are rigidly connected t0- gether through the hollow piston rod 24 `in close coupled electrical connection with each other andy in accurate alignment through this rigid tandem mounting and the axial guiding means just now described. l

The accumulator device Qz ot the quenching mechanism Q as located in the lower part of column 2l consists of a tank 0| previously mentioned in connection with lthe discharge from the quenching unit Q contained in the mounting mechanism M, which tank receives discharge quenching medium such as oil, water or other, and stores it for use. This tank is provided with a cooling coil |34 having suitable connection |35 and thence downwardly l with a source oi cooling iluid as, for example, water from the water mains. Alongside of the tank is an accumulator cylinder |38, the piston.

|31 o1' which is .biased to a downward position by a. great weight |38 on the upper and outer end of piston rod |33. Oil is admitted to the cylinder from the tank 5| through check valve |33 and filter 200 and discharged Vfrom the cylinder through check valve 20| and discharge pipe 202. The charge of oil is drawn in by downward movement of the piston |31 underV the force of the weight. |33 and discharged by upward movement of the piston under force of compressed air admitted to the bottom of the cylinder under the piston through a valve 203 from a compressedair supply pipe 204, valve 203 being biasedV in ,closed position and arranged to be opened upon energlzation of valve actuating magnet |91.

'I'he accumulator |35 -being so charged andY its pressure sustained by the accumulator weights |33, that quenching iluid is admitted through connection |23 at the v-propertlme in the operation of the machine through electromagnetic valve 203. When the quenching iiuid is so admitted to the hollow piston rod 25 it passes down to the spray. head Q whereit is discharged as a spray to the workpiece.

Where the modiiled form of`spray head shown in Figure 9 is used, the spray apertures remain l tering and aligning head Y|30a corresponding to A previously described at |30. It is'held against axial rotation by a pin andslot connection 233,V

234. Normally when quenching iluid pressure is removed from rodk 25aof the quenching unit through theatmospheric venting action of the electro-pneumatic valve 203, the inner sleeve 2|2 occupies Ythe raised position `as shown in Figure 9, but when the pressure is applied through valve 203 and from the accumulator |36, sleeve 2|2 is moved downwardly against the pressure of spring 232 to bring the inner sleeve apertures |5| correspondingin number and angular relation to the apertures '223 of, the outer sleeve 2li into register with the said apertures 229, permitting the quenching spray to be directed upon the surface 54 to .be quenched. The spray continues at the predetermined pressure of the accumulator y |36 and until the predetermined volume ofthe accumulator |38 is exhausted, thereby insuring the regulated quantity and pressure ot quenching medium.

'The control mechanism C for the machine is mounted in its entirety on a shell |53 in the upper end oi' the column 20. 'I'he construction and operation of this control mechanism C is that which is described in my copending application Serial No. 96,346 and therefore need not be described ln detail here.

When a workpiece is put in place a cycle of operation is started and during the early stages of the cycle, as set forth in my copending application Serial No. 96,346,'energization of the control valve H0 causes air to be admitted to the top of the cylinder IIS which moves the piston rod 25 and the sprayhead H8 into operative relation with the workpiece, this position being indicated in Figure 3.

The electromagnetic control valve HI is next energized which admits air to the top of cylinder which eilects movement of the heating coil 03 into operative relation with the workpiece, which position is shown in Figure 4. Thereafter the switch in the control mechanism C closes the high-frequency power line leading to the terminals of the primary coil 89 of the transformer. The secondary transformer coil BI having been brought into transformer relation with the primary coil upon the movement of the heating coil 63 into operative relation with the workpiece, the heating coil 63 is supplied with highfrequency current of the proper volume to effect the desired heat treatment of the work in a predetermined period of time.

At the end ol.' the heating period the power switch actuates to deenergize the primary winding of the transformer. Simultaneously therewith the electromagnetic control valve H4 causes admission of air to the bottom of cylinder H0, quickly moving the coil 89 out of association with the workpiece, and the secondary winding I4 of the transformer out of inductive relation with the primary winding 99.

Immediately after the upward movement of the heating coil and the transformer secondary, quenching iluid is ejected through the spray head ||9 over the heat treated surface of the workpiece, the duration of the quench being under the control of the mechanism C.

While the heating unit H is in the operative position shown in Figures 4 and 6, and energized by the high-frequency current supplied through the transformer switching mechanism T, currents of considerable magnitude are induced in the adjacent section of the hub 26 and concentrated at and near the inner or bearing surface, raising the temperature in an inner annular zone substantially of the depth and length indicated by dotted line |05 in Figure 6, to the desired heat treating temperature.

As soon as suilicient heating has occurred, the heating unit H is withdrawn leaving the spray head ||9 in the position shown in Figure 7, immediately after which the work is quenched by the spray of quenching fluid ejected through the spray head against the work as indicated in Figure 7. In the present example where quenching iluid is a liquid, the volume and rate of now is made suillcient to overflow the hub interior and over and around the exterior of the hub as indicated in Figure 3. The work being suitably quenched, the spray head is withdrawn upwardly from the workpiece leaving the workpiece in the desired heat treated condition in the annular zone indicated by the dotted line in Figure 6.

It will be noted from Figures 4 and 6 that with the heating unit iny operating position within the hub 20, the inwardly offset lower end portion of the magnetic ring 10 ilts within the rabbeted portion in the upper end of the hub substantially filling the gap in the magnetic circuit between the upper end of the laminated core element of the heating unit and the upper end of the hub 2C. The lower end of the magnetic ring 10 by thus completing the magnetic circuit through its body material of low reluctance, maintains the path of the magnetic ilux'through the core of the heating element and the work to be treated at the smallest possible or minimum reluctance with consequent increase in eiliciency. As the heating coil is withdrawn from the work moving out of the surrounding held of low reluctance afforded by the surrounding iron of the hub, it moves into the ring 1l of magnetic material, thus preventing undue change in its magnetic reluctance and thereby avoiding substantial variation in the power factor characteristic of the circuit.

The modification shown in Figures 9 and 10 is very similar to the heating element shown in the preceding figures except that the magnetic ring or sleeve 201 is built up of tapered radial laminations, certain improvements are made in the arrangement of channel 209 for circulation of the cooling iluid, the fluid connection 2|0 for the lower terminal of the heating coil is varied in the interest of simplicity of assembly, and the spray head 2|| provided with a pressure-operated valve 2| 2. The laminations comprising the magnetic sleeve 209 are tapered and arranged radially in a manner similar to the arrangement of the tapered, radial laminations of the magnetic cores of the heating coil and transformer previously described, and are held in assembled relation as shown by the upper and lower clamping rings 2li and 2|! clamped together by sets of clamping bolts 2li and 2| 6, the clamping rings being provided with annular wedge rings 2|1, 2|! which engage complementary notches in the laminations constituting the magnetic ring 209. The small winding 2|9 has no electrical function in the assemblage, but is simply a binding wire or cord having the purely mechanical function of holding the laminations of the sleeve 208 in assembled relation especially during assembly of the parts. The several short and long bolts 2|5, 2|6 are alternated about the structure, the long bolts 2H serving also to clamp the bearing ring 220 on to the top of the magnetic sleeve assembly, the bearing ring 220 bearing at its inner surface against the cylindrical surface 22| of the inner cylindrical supporting member 222.

'I'he cooling liquid, return channel 209 through the piston rod 24a is simpliiied by providing it in the form of a long bore passing upwardly from l the lower end of the piston rod 24a intermediate the inner and outer walls thereof, the bottom of the bore being closed by a suitable stop plug 223.

` channel 221 of the piston Connection is made between this channel 209 and the lower terminal end 224 of the heating coil, through a sector-shaped plug 2 l0 inserted in the lower end of the laminated core of the heating 1cgil alrlid pn'livictiel with a channel 226 connecting e c anne a e end of the heatin the channel 229. g con with The pressure-operated valve 2|2 in the s head 2| is in the form of a hollow cylindrr-)irci valve element closed at the bottom and open at the top for communication with the channel 221 in the pilot arbor H9. The valve member 2 i2 is provided with a suitable number of ports |5| corresponding in number to the number of'spray holes 229 in the spray head 2|I .and arranged to register therewith to connect them with the rod u mov the valve from the normal closexdogositinnlv to its lowermost position at which it is stopped by engagement of the outer bottom portion 220 of the valve element with the upper end 29| of the pilot head Illa. A compression spring 232 urges the valve element 2|2 upwardly against stop pin 239 fixed in the cylindrical wall of talig spray head and passing through axially extending slots 224 in the upper end of the valve element 2|2, the pin slidably engaging the surfaces of such slots to maintain the ports in the sliding valve element 2l! in proper angular relation with the spray openings in the spray head.

While the operation herein described for the purpose of disclosure is one for eilecting a hardening of the bearing race portion of an automobile wheel hub, it is to be understood that other forms of heat treatment andthewheat treatment of various other objects may be ac` complished by suitablev variation` in the cycle of operations or the relative timing ofthe dill'erent phases of the cycle, or `by suitable adjustments or modiilcations of the apparatus.

It is also to be understood that while I have shown and described certain speciilc embodiments and modes of operation of myinvention for the sake of disclosure, the invention is not limited to such speciilc embodiments andmodes of operation but contemplates all such variants and modications thereof as fall fairly within the scope of the appended claims.

What is claimed is: v

1. Apparatus for heat treating hollow objects from the inside by electric inductive heating comprising a central pilot member arranged to be extended into the hollow of the object to be heat treated and positioned in fixed relation therewith and an inductive heating coil mounted around and adapted to slide along said pilot member into operative relation with the interior of said hollow'object.

2. An inductive heating unit comprising a hollow cylindrical support, a cylindrical core element mounted about said support, a tubulareconductor wound in a cylindrical coil about said core, said tubular conductor extending from one end of the coil beyond the other end thereof, said cylindrical support having a enamel extending longitudinallythrough its wall from near said other end of the coil to a point beyond the ilrst-mentioned end of the coil, a conduit element of electrical conducting material inserted in the core between the said other end of the coil and said support, said conduit element having a channel connecting the channel of the tubular conductor at the said other end of the coil with the channel in the wall ofthe cylindrical support, and a tubular electrical conductor electrically connected with said cylindrical supportand in iluid conducting connection with said channel in the wall of the cylindrical support.

3. Apparatus for heat treating hollow objects from the inside and which have a centering aperprising a pilot member arranged to be extended into the hollow of the object to be heat treated in fixed relation therewith in said centering aperture, an inductive heating coil mounted to slide along said pilot member into operative relation with the interior of ysaid hollow object, a protect; ing Vmagnetic sleeve axially slidably mounted around said induction heating coil, and a spring Vurging said sleeve into protecting relation with laid coil.

' workpiece causes said sleeve to slide out of protecting relation of said coil.

6. In-an apparatus for heat treating metallic objects by electric inductive heating, a support sleeve, a plurality of radially tapered iron lamina- `tions secured on said sleeve, said laminations being shaped so that in assembled relation they form a spool, a helical inducing coil on said spool, said coil being insulated from said spool,`

said spool having a sector-shaped segmental portion cut away to iorm a recessat least at one end and a complementary insulating block inserted in said recess, a connection from one end of the coil extending Vthrough said block, an annular Aaxially extending ridge associated with Vsaid sleeve, and a mating annular groove in said laminations and block engaged by said ridge to secure the laminations and block inV assembled relation. n

7. Apparatus for heat treating a surface por-V tion of an object of magnetic material by elec'- tromagnetic induction comprising an inducing coil, means. for eilecting relative movement between the object and thecoil to bring them into inductive relation and` with the coil extending beyond one end of the object, an annular substantially continuous ilux-conducting 'element composed of magnetic material arranged to be moved into abutting relation with said one end of the object to form an end extension thereof extending beyond the coil upon relative movement of said coil and object into inductive relation, and resilient means urging said ux-conducting element into inductive relation with substantiallyl the entire length of the coil.

8. In an apparatus for heat treating metallic objects by electric inductive heating, a support sleeve, a plurality of radially tapered iron lami.r

nations secured on said sleeve, said laminations being shaped so that in assembled relation they form a spool, a helical inducing coil on` said spool,

i said coil being insulated from said spool, said spool having a sector-shaped segmental portion cut away to form a recess at least at one end and a complementary insulating block inserted in said recess and a connection from one end of the coil extending through said block, said spool formed from said laminations and blockhaving an ,annular notch at each end adjacent said sleeveand means on said sleeve for engaging said annular notches to secure the spool in assembled relation.

9. In apparatus lor heating a surface portion of 'a workpiece of magnetic material by v'electromagnetic induction, a support, anv open iluxlconducting member carriedV by said support, an inducing coil concentric with said flux-conducting member, a second linx-conducting member concentrically arranged with respect to said coil and ilrst` member and being carried by said support, said coil, said members and said support l constituting a unitary structure, and means ior effecting relative movement between said unitary structure and the workpiece adapted to be heated to position said workpiece and unitary structure in inductive relation, said second flux-conducting member being adapted iny said position of inductive relation to form an end extension of the workpiece adapted to be heated and comprising part of the magnetic circuit of said coil in series with said first flux-conducting member and the workpiece to be heated.

10. In apparatus for heating a surface portion of a workpiece of magnetic material by electromagnetic induction, a support, an open fluxconducting member carried by said support, an inducing coil concentric with said member, a second flux-conducting member concentrically arranged with respect to said coil and first member and being carried by said support, said second member being axially movable relative to said coil and first member and normally being coextensive with a substantial portion of said coil and first member, said support, coil and members constituting a unitary structure, and means for effecting relative movement between said unitary structure and the workpiece adapted to be heated to position the workpiece adapted to be heated and said structure in inductive relation, said second ux-conducting member being engageable with an end of the workpiece to form an end extension thereof and movable axially away from said coil and first member upon such engagement and during such relative movement into inductive relation.

1l. Apparatus for heat treating hollow objects from the inside by electric inductive heating, comprising an annular open core of magnetic material and an inductive heating coil surrounding said core, said core Aand coil being arranged to be positioned within the hollow of the object to be heated, a central support extending coaxially within said core for supporting the same, and an annular member of magnetic -material supported on said central support concentric with said coil and core and being adapted to form an end extension of the object to be heated, the magnetic circuit of said coil being composed substantially in its entirety of said core and annular member in series with the object to be heated, said support, coil, core and annular member constituting a unitary structure.

12. In apparatus for heating a surface portion of a workpiece by electromagnetic inductie an inductive heating head comprising an annular core of magnetic material; a hollow inducing coil mounted upon said core, a tubular supporting member extending within said core in core-supporting relation, means within said tubular member and forming with a portion of the inner surface of said tubular member, a coolant-passageway, and a hollow connection between said coil and coolant passageway for the flow of coolant therebetween.

13. In apparatus for heating a surface portion of a workpiece by electromagnetic induc tion, any

inductive heating head comprising an annular core of magnetic material, a hollow inducing coil mounted upon said core, a tubular supporting member extending from one end of said core to the other end thereof, means within said tubular member and forming therewith a longitudinally extending passageway, one end of said passageway terminating near said other end, means connecting said one end of said passageway with the adjacent end of said coil for the transfer of coolant between said passageway and coil, a coolant-conducting means for the other end of said coil, and a coolant-conducting means for the other end of said passageway.

14. In apparatus for heating a surface portion of a workpiece by electromagnetic induction, an inductive heating head comprising an annular core of magnetic material, a hollow inducing coil mounted upon said core, a tubular supporting member extending within said core in core-supporting relation, means within said tubular member and forming with a portion of the inner surface of said tubular member a coolant passageway, and a hollow connection between said coil and coolant passageway for the flow of coolant therebetween, said tubular member and said hollow connection being of'electric current-conducting material.

15. In apparatus for heating a surface portion of a workpiece by electromagnetic induction, an inductive heating head comprising an annular core oi' magnetic material, a hollow inducing coil mounted upon said core, a tubular supporting member extending from one end of said core to the other end thereof, means within said tubular member and formmg therewith s longitudinally extending passageway, one end of said passageway terminating near said other end, means connecting said one end of said passageway with the adjacent end of said coil for the transfer of coolant between said passageway and coil, a coolant-conducting means for the other end ot said coil, and a coolant-,conducting means for the other end of said passageway, said tubular member, connecting means and both said coolantconducting means being of electric current-conducting material.

16. In apparatus for heating the inner surface oi' a hollow workpiece by electromagnetic induction, an induction heating head comprising a central supporting member, an annular open core coextensive with and coaxially carried by said supporting member, an inducing coil surrounding said core and being supported thereby, said core shielding said supporting member from the inductive heating eiiect of said coil, an annular member of magnetic material carried by said support coaxial with said core and coil and having a ilxed internal diameter throughout its length substantially greater than the external diameter of said coil, and means for axially moving said supporting member to position said core and'ooil into inductive heating relation with the inner surface of the workpiece to be heated and position the annular member of magnetic material against the end of the workpiece to be heated to form an end extension thereof, the magnetic circuit of said coil being comprised substantially in its entirety of said core and annular member in series with the workpiece to be heated.

11. In apparatus for heating a surface portion of a workpiece of magnetic material by electromagnetic induction, a support. an open flux-conducting member carried by said support, an inducing coil concentric with said flux-conducting member, a second flux-conducting member oon- -centrically arranged with respect to said coil and first member and being carried by said support, said coil, said members and said support constituting a unitary structure, and means for eiiecting relative movement between said unitary structure and the workpiece adapted to be heated to position said workpiece and unitary structure in inductive relation, said second iiux-conducting member being adapted iny said position of inductive relation to form an end extension of the workpiece adapted to be heated and comprising part of the magnetic circuit of said coil in series with said first flux-conducting member and the workpiece to be heated, said support being elec trically connected with one end of said coil to yserve as a bus bar therefor.

18. In an apparatus yfor heat treating metallic objects by electromagnetic induction. a support, an annular core comprised of a plurality ofradially tapered laminations ot magnetic material. having a substantially ooextensive sector-shaped recess, and a complemental block oi' insulating material in said recess, means engaged with said laminations for holding Said laminations and block in annularly assembled relation on said support, and an inducing coil carried by said core,

said coil having an electrical connection extending through said insulating block.

' HOWARD E. soMEs. 

